Method of forming a piston and like components



Jan. 26, 1965 J. B. SCANNELL METHOD OF FORMiNG A PISTON AND LIKECOMPONENTS Filed Nov 2, 1960 United States Patent Ofiice 3,166,832NIETHOD OF FORMING A PISTON AND LIKE COMPONENTS John B. Scannell, DrexelHill, Pa., assignor to Greene, Tweed & Co., North Wales, Pa. Filed Nov.2, 1960, Ser. No. 66,778 14 Claims. (Cl. 29156.62)

This invention relates to methods of forming pistons and likecomponents.

In the practice of Pat. No. 2,420,104 and methods leading to likearticles of manufacture, one basic problem is encountered which is quitesignificant.

To understand this problem, it is first necessary to consider thestructure which it is desired be prepared; to wit: a substantially rigidbody having a surface groove in which are positioned a resilient ringand at least one substantially rigid backup ring which functions tomaintain the position of the resilient ring and to prevent extrusionthereof.

Snapping the resilient ring into position in the groove is a relativelysimple operation and presents no great problem. However, positioning therelatively rigid ring is diflicult since it will generally not have theelastic properties necessary. It is therefore necessary to split therigid ring in order that this ring can be slipped over the piston intothe groove. Unfortunately, the position at which the rigid ring is splitconstitutes the weak and probable failure point of the seal.

It is an object of the invention to avoid this problem and incontemplation thereof, the invention considers cutting the rigid ringdirectly out of the body of the piston, in situ, so that on itsformation the ring is already in proper position.

Other objects, as well as features and advantages of the invention, willbe found in the following detailed description of a preferred embodimentillustrated in the accompanying drawing in which:

FIGURE 1 diagrammatically illustrates the processing of a work pieceaccording to the invention to form the finished article of manufactureof the invention;

FIGURE 2 diagrammatically illustrates a first step of the method of theinvention;

FIGURE 3 diagrammatically illustrates a second step of the method of theinvention;

FIGURE 4 diagrammatically illustrates the next sequential stepcontemplated by the invention;

FIGURE 5 illustrates a sub-assembly, the structure of which is formedaccording to the steps illustrated in FIGS. 24;

FIGURE 6 illustrates a completed assembly prepared according to themethod of the invention;

FIGURE 7 illustrates a further application of the invention wherein thebackup ring is given a different relative position; and

FIGURE 8 illustrates the structure of FIG. 7 with the resilient ring inplace.

To facilitate an explanation of the method of the invention, it will befirst assumed that it is desired to prepare a piston of cylindrical formhaving therein an annular peripheral groove of substantially trapezoidalcross-section, wherein are located two backup rings of substantiallytriangular cross-section and adapted to sandwich therebetween aresilient ring of O or D cross-section. It will be understood, however,that variations of these shapes and elements are possible within thescope of the invention, as will become apparent hereinafter.

In FIGURE 1 is indicated a workpiece 19 at the end of which is indicateda cylindrical portion 12 which is ultimately severed from the main bodyof the workpiece. The workpiece may be, for example, of plasticmaterial, such as nylon or polytetrafluoroethylene, or the like.Generally the workpiece will be selected to have a diameter slightlygreater than that of the final piston diameter desired. The workpiece isthen in the vicinity of end portion 12, finished to the desired diameterand provided with a flat end face 14.

Three tool cuts are then made with three tools or with the same toolmoved to different positions, the tools being generally indicated at 16,18 and 20. Tool 16 is fed into the end portion 12 at the desired angle,to generate cut 22 (see FIG. 2).

Cut 22 is an annular cut which is formed either by rotating theworkpiece 10 or by holding the workpiece 10 steady in position Whilerotating the tool 16 thereabout. The thickness of tool 16 and theresulting width of the groove 22 is selected in accordance with aspectsof the invention which will be discussed hereinunder.

Secondly, a'second groove 24 (see FIG. 3) is cut into the end portion 12in a manner similar to that employed for groove 22. The width of tool 20and the resulting width of groove 24 is also important, as will bediscussed hereinunder.

It is important to note that grooves 22 and 24 are in intersectingrelationship with one another, or are, in other words, inclined withrespect to each other. These grooves thus form an annular body or rib 26of substantially trapezoidal cross-section which remains aflixed to theend portion 12.

Following the formation of grooves 22 and 24, a further cut 28 (see FIG.4) is made in the rib 26, so as to sever the same from the portion 12and form two separate rings 30 and 32. These rings are annular rings,each being of substantially triangular cross-section, inasmuch' as thewidth of tool 18, and thus of cut 28, is selected so as to remove thecentral portion of the trapezoidal cross-section of the rib 26.

It is to be noted that the accumulated widths of tools 16, 18 and 20 areselected so as to provide a suitable distance between the inner-faces ofthe resulting annular ring-confining cavity 34, which in its final formis of substantially trapezoidal crosssection. It will also be noted thatrings 30 and 32 can be moved away from each v other by amountscorresponding to the widths of grooves 22 and 24 so as to providetherebetween a space 36 which is adapted to accommodate a resilientsealing ring.

It will be appreciated that rings 30 and 32 are fabricated from the verysame material as is the piston 12 itself and that these rings aresubstantially locked in position, due to the rigidity of the materialfrom which they are fabricated.

FIGURE 1 further illustrates the formation of a hole or bore 38, whichis formed in the piston 12, so as to accommodate the insertion of apiston rod. The final form of the article of manufacture contemplated bythe invention is illustrated in FIGURE 6.

In FIGURE 6 is indicated in axial section a cylinder 40, wherein isslideably accommodated the piston 12; Rings 30 and 32 are shownpositioned in the cavity 34 and a resilient 0 ring 42 is shownaccommodated between rings 30 and 32 within the space 36.

A piston rod 44 is provided with a threaded end 46, which is insertedthrough the bore 38, there being provided on opposite faces of thepiston 12 washers 48 and 50. Finally, a nut, or like member 52,threadably engages the threaded portion 46 of the piston rod 44, to lockthe piston in position on the piston rod.

Thus in one form the method of the invention consists of forming apiston by cutting out of a cylindrical piston body and in situ at leastone annular ring, or, alternatively, of cutting into a cylindrical bodyat least two grooves in intersecting relationship which form in situ anannular ring.

More specifically, the invention contemplates forming Patented Jan. 26,I965 a piston body and cutting in.o the same first and second peripheralgrooves inclined towards each other, to form in this body an annular ribof trapezoidal cross-section, which is connected to the body. Then thereis contemplated, according to the method of the invention the cutting ofsaid rib into two separate parts and severing the same from the body toform two rings adapted to constitute backup rings.

As noted above, the body may preferably be of a plastic material, suchas nylon or polytet-rafiuoroethylene, and between the backup rings isaccommodated a resilient sealing ring of known type.

Preferably, the rings are first formed as a single rib of trapezoidalcross-section, connected to the associated body, this connected bodybeing severed such that the middle portion of the trapezoid is removedto form two backup rings of triangular cross-section.

It will be noted that the backup rings have substantially the same meandiameter as the mean diameter of the groove in which they areaccommodated, so that the backup rings are secured or locked in positionas they are formed.

In FIGS. 7 and 8, the backup ring is provided internally, a backup ring60 being cut out in situ. In connection with this embodiment, one cut 62is made radially into member 63 and a second cut 64 is made inintersecting relation with the first cut. The ring 60 is moved to theextreme position of FIG. 8 and a resilient ring 66 is placed in theresulting annular groove.

There will now be obvious to those skilled in the art many modificationsand variations of the method and article of manufacture set forth above.These modifications and variations will not, however, depart from thescope of the invention it defined by the following claims.

What is claimed is:

1. In method of manufacturing a piston adapted for accommodating apiston ring, the steps comprising forming a piston body, cutting intothe surface of said body first and second peripheral annular groovesinclined towards each other to form in said body an annular rib oftrapezoidal cross-section connected to the body, and cutting said ribinto two separate parts and severing the same from said body to form tworings each of which are completely disconnected from said body and areadapted to constitute backup rings for the piston ring.

2. A method as claimed in claim 1 comprising forming said body ofaplastic.

3. A method as claimed in claim 2 wherein the plastic is nylon.

4. A method as claimed in claim 2 wherein the plastic ispolytetrafluoroethylene.

5.. A method as claimed in claim 1, further comprising snapping aresilient piston ring into position between the backup rings.

.6. A method as claimed in claim 1 comprising removing a central portionof the rib of trapezoidal cross-section by cutting said annular rib sothat the thus formed backup rings have a triangular cross-section.

7. A method as claimed in claim 1 comprising boring a hole through saidbody to accommodate a piston rod.

8. A method as claimed in claim 7 comprising inserting a threaded pistonrod into said hole and sandwiching said body With Washers and a nut tolock said body to said rod.

9. A method as claimed in claim 1 comprising cutting said peripheralgrooves with a width adapted to provide, with the cutting of saidannular rib, an annular ring-confining cavity of predetermineddimensions in said piston.

10. A method as claimed in claim 1 wherein said body is cylindrical.

11. A method as claimed in claim 1 wherein said body is part of a largerpiece from which it is severed when the backup rings are formed.

12. A method of forming a piston comprising providing a piston body andforming two intersecting peripheral annular grooves in the surface ofthe body one being substantially normal to the 3X15 of the body to forma completely severed annular ring capable of free movement in an annularring-c0nfining cavity which is defined by the surfaces of the bodybounding the grooves whereby the ring is adapted to constitute a backupsupport for a resilient annular element inserted into saidring-confining cavity.

13. A method of forming a piston comprising forming a piston body,cutting into the surface of said body, first and second annularperipheral grooves inclined towards each other to form in said body anannular rib connected to said body in an annular ring-confining cavitydefined by the surfaces of the piston body bounding said grooves,completely severing said rib from said body to form rings which havelimited movement in the cavity and snapping an annular resilient elementinto position in the cavity of said body to engage said annular ringsformed therein and be held in position thereby.

14. A method of forming a piston comprising forming a cylindrical pistonbody, cutting into the surface said body, first and second peripheralannular grooves inclined towards each other to form in said body anannular rib of trapezoidal cross section connected to the body in anannular ring-confining cavity defined by the surfaces of the piston bodybounding said grooves, cutting said rib into two separate parts andcompletely severing each part from the body to form two annular ringsWhich are freely slidable in said cavity, and snapping an annularresilient element between the two said rings such that said rings engagethe resilient element on either side thereof and hold the same immovablyin position in said cavity.

References Cited in the file of this patent UNITED STATES PATENTS1,224,239 Underwood May 1, 1917 1,328,182 Miller Jan. 13, 1920 2,003,440Harrison June 4, 1935 2,420,104 Smith May 6, 1947 2,635,331 HarbisonApr. 21, 1953 2,830,358 Millen Apr. 15, 1958 2,886,034 Robinson et alMay 12, 1959

2. IN METHOD OF MANUFACTURING A PISTON ADAPTED FOR ACCOMMODATING APISTON RING, THE STEPS COMPRISING FORMING A PISTON BODY, CUTTING INTOTHE SURFACE OF SAID BODY FIRST AND SECOND PERIPHERAL ANNULAR GROOVESINCLINED TOWARDS EACH OTHER TO FORM IN SAID BODY AN ANNULAR RIB OFTRAPEZOIDAL CROSS-SECTION CONNECTED TO THE BODY, AND CUTTING SAID RIBINTO TWO SEPARATAE PARTS AND SEVERING THE SAME FROM SAID BODY TO FORMTWO RINGS EACH OF WHICH ARE COMPLETELY DISCONNECTED FROM TWO RINGS EACHOF WHICH ARE TO CONSTITUTE BACKUP RINGS FOR THE PISTON RING.